The invention relates to a vacuum valve comprising a valve housing with a valve opening that has an axis, a valve seat that surrounds the valve opening and has a first seat main section and a second seat main section, with these sections being offset relative to each other in the direction of the axis of the valve opening and being connected to each other by first and second seat connecting sections, a closing element that can be moved in a straight line in a closing direction at an angle to the axis of the valve opening from an open position, in which the valve opening is exposed, into a closed position, in which the valve opening is sealed, and against the closing direction from the closed position into the open position. At least one peripheral, closed seal that is arranged on the closing element and has the first and second seal main sections allocated to the first and second seat main sections and the first and second seat connecting sections and first and second seal connecting sections and extends in a groove that is bounded, viewed in cross section, by two side walls and one base wall, wherein the first seal main section is arranged on a front end face of the closing element with respect to the closing direction and has a middle part in which the seal runs in a straight line.
In vacuum installations in which belts are processed that are made from, in particular, a film material and are unwound from a roll and rolled up onto a roll after processing, the problem arises that the rolls must be replaced after they are completely unwound or wound up. For this purpose, they are arranged in separate vacuum chambers that can be separated by valves from the vacuum chambers in which the processing is performed. In this way, the valve can be closed against the material of the continuous belt. Therefore it can be avoided that the entire vacuum installation must be flooded when each roll is replaced. For this purpose, a slanted seat valve is typically used as the vacuum valve in which, for closing the vacuum valve, a closing element is guided in a straight line against a seat standing at an angle to the axis of the valve opening. One disadvantage here lies in that, among other things, the material of the belt is bent when the valve is closed.
Vacuum valves of the type noted above are known, for example, from U.S. Pat. No. 4,809,950, U.S. Pat. No. 4,881,717, U.S. Pat. No. 5,909,867, and U.S. Pat. No. 6,685,163. These valves have a simple configuration, can be closed and opened quickly by just a straight-line movement of the closing element (in contrast to, for example, L-shaped movements of the closing element for other valve types), wherein nevertheless transverse forces on the seal are avoided during the closing of the closing element and relatively few particles are released during the closing and opening process.
For these vacuum valves, the seal is typically arranged on the closing element and is pressed against a sealing face on the seat of the vacuum valve in the closed state of the vacuum valve. Usually, the seal is vulcanized on the closing element, wherein the maintenance expense is increased after wear of the seal. A seal arranged in a groove of the closing element and shaped in the form of an O-ring is likewise already known for this type of valve.
For the previously known slanted seat valve used in belt-coating installations, for better sealing, when the valve is closed against a conducted belt, a peripherally closed seal is arranged on the end both on the closing element and also on the valve seat. When the valve is closed without the conducted belt, then the seals are pressed against each other on the closing element and on the valve seat. If the valve is closed with a belt passed through the valve opening, then sections of the seals are pressed against the belt on both sides. The width of the belt is here less than the extent of the peripherally closed seals, so that sections of the seals lying next to the belt on both sides are pressed against each other.
For static seals by which two parts of a valve housing of a vacuum valve are connected to each other in a sealed manner, it has already become known to arrange the seal in a groove in which one of the two side walls of the groove is formed by a clamping bar that is screwed onto the part of the valve housing having the seal. Through such a construction, previously the configuration of an undercut groove for holding an O-ring could be simplified. With modern CNC milling machines, the configuration of an undercut groove in a solid part can be performed easily, so that the configuration with a clamping bar is more complicated and expensive.
For a sliding valve in which two valve plates of the closing element are spread apart from each other in the closed state of the vacuum valve, in order to press seals held on the plates against opposing seal faces surrounding the valve openings, a configuration of the valve plate made from bent sheet-metal parts has furthermore become known. On the corresponding valve plate, an O-ring is clamped between a bent edge of the valve plate and an annular holding element that has a bent configuration in cross section and is connected to the valve plate by spot welding. In this way, a groove holding the O-ring has been formed for a valve plate consisting of a bent metal sheet.
From U.S. Pat. No. 6,899,316, a vacuum valve emerges in which a valve plate is moved starting from an open position in which it releases the valve opening via an intermediate position in which it covers the valve opening, but is lifted from the valve seat, into a closed position pressed against the valve seat. For adjustment between the open position and the intermediate position, a first drive is used that shifts a carrier unit carrying the valve plate in a straight line. For adjustment between the intermediate position and the closed position, at least one piston-cylinder unit formed by the carrier unit is used, wherein a piston can be shifted in a cylinder recess of the carrier unit. The piston rod that carries the valve plate is sealed relative to the carrier unit by first and second seals, in order to reliably seal the excess pressure that is elevated relative to atmospheric pressure introduced into the cylinder space for adjusting the valve rod relative to the vacuum region of the vacuum valve. A channel that is connected to the atmosphere or can be evacuated opens into the space enclosed by the two seals, wherein the security of the seal relative to the excess pressure present in the cylinder space is further improved.